Bipolar separator assembly for fuel cells and method of making same

ABSTRACT

A bipolar separator assembly for use with a fuel cell comprising: a plate member having opposing first and second surfaces compatible with fuel gas and oxidant gas, respectively, the plate member having first and second opposing end segments and third and fourth opposing end segments which are transverse to the first and second opposing end segments; first and second pocket members situated adjacent the first and second end segments and extending outward of the first surface, the first and second pocket members being adapted to enclose opposing ends of an anode current collector, and third and fourth pocket members situated adjacent the third and fourth end segments and extending outward of the second surface, the third and fourth pocket members being adapted to enclose opposing ends of a cathode current collector, wherein at least a portion of each of the first, second, third and fourth pocket members is formed separately from the plate member and is releasably positioned relative to the plate member.

BACKGROUND OF THE INVENTION

This invention relates to a bipolar separator assembly and, inparticular, to a bipolar separator for use in molten carbonate fuelcells.

A fuel cell is a device that directly converts chemical energy in theform of a fuel into electrical energy by way of an electrochemicalreaction. In general, like a battery, a fuel cell includes a negativeelectrode or anode and a positive electrode or cathode separated by anelectrolyte that serves to conduct electrically charged ions betweenthem. In contrast to a battery, however, a fuel cell will continue toproduce electric power as long as fuel and oxidant are supplied to theanode and cathode, respectively. In order to produce a useful amount ofpower, individual fuel cells are typically arranged in stackedrelationship in series.

In molten carbonate fuel cells, an electrically conductive bipolarseparator is used to separate adjacent cells in a fuel cell stack. Themain functions of a bipolar separator of molten carbonate fuel cells areto separate cathode gas from the anode gas and to provide currenttransmission and load pressure distribution in high temperaturecorrosive environment. A typical bipolar separator comprises a thin flatmetal plate member, or separator sheet, having first and second opposingsurfaces which form active areas and which are compatible with oxidantand fuel gases, respectively. First and second opposing ends of theseareas are folded upward and toward each other to form first and secondpockets. Third and fourth opposing ends of the areas are folded downwardand toward each other to form third and fourth pockets. The first andsecond pockets support a fuel cell matrix on the first surface side ofthe plate member, while third and fourth pockets support a fuel cellmatrix on the opposing second surface side of the plate member. In thisway, the first, second, third and fourth pockets form wet seals for themolten carbonate fuel cells that seal both the separator sheet and thematrix and create flow fields for the fuel and oxidant gases.

In order to realize long-term stability of the fuel cell, the wet sealsand edges of the separator sheet must be kept corrosion free. Inaddition, corner areas of an externally manifolded fuel cell stack arecritical for sealing to the manifold and thus, typically need to be asflat as possible. U.S. Pat. No. 6,372,374, assigned to the same assigneeherein, discloses a bipolar separator with improved wet seals in whichthe wet seals are made separately from the separator sheet and are thenwelded to the separator sheet during the assembly process. In theconfiguration disclosed in the '374 patent, the anode and cathodecurrent collectors extend into the pockets formed by the attached wetseals, which provide uniform support to the electrodes and the matrix.These features of the bipolar separator are important to the performanceof the fuel cell system.

When the bipolar separator of the '374 patent is manufactured andassembled, the five components of the separator, i.e. one plate memberand four wet seal pockets, have to be welded together. The welding ofthese components results in a weld around the entire perimeter of thebipolar separator, which in typical fuel cells is about 160″ of weld. Inaddition, portions of this weld extend in the corner areas of the fuelcell stack, which, as mentioned above, are critical for sealing andsupporting the external manifolds against the fuel cell stack. However,the welding process is difficult and costly. In addition, to obtainconsistent results, it is necessary to weld the wet seal pockets to theplate member before the corrugated current collectors are in place whichallows for properly fixturing with chill-blocks. Since the corrugatedcurrent collectors extend under the wet seal pockets, the currentcollectors need to be deformed and manipulated in order to slide theminto place. However, this process requires several people to perform andis very difficult to automate effectively.

Therefore, it is an object of the present invention to provide a bipolarseparator assembly which includes wet seal pockets made separately fromthe plate member but which does not require welding around the entireperimeter of the bipolar separator in order to attach the wet sealpockets to the plate member.

In addition, it is a further object of the present invention toeliminate manual manipulation and installation of the corrugated currentcollectors into the bipolar separator, and in particular, into the areasunder the wet seal pockets of the bipolar separator.

SUMMARY OF THE INVENTION

The above and other objectives are realized in a bipolar separatorassembly for use with a fuel cell comprising: a plate member havingopposing first and second surfaces compatible with fuel gas and oxidantgas, respectively, the plate member having first and second opposing endsegments and third and fourth opposing end segments which are transverseto the first and second opposing end segments; first and second pocketmembers situated adjacent the first and second end segments andextending outward of the first surface, the first and second pocketmembers being adapted to enclose opposing ends of an anode currentcollector, and third and fourth pocket members situated adjacent thethird and fourth end segments and extending outward of the secondsurface, the third and fourth pocket members being adapted to encloseopposing ends of a cathode current collector, wherein at least a portionof each of the first, second, third and fourth pocket members is formedseparately from the plate member and is releasably positioned relativeto the plate member. The first end segment of the plate member forms afirst portion of the first pocket member and the second end segment ofthe plate member forms a first portion of the second pocket member, anda second portion of each of the first and second pocket member is formedseparately from the plate member and is releasably secured to therespective first or second end segment of the plate member. In addition,the third and fourth pocket are formed separately from the plate memberand are releasably positioned adjacent the third and fourth end segmentsof the plate member, respectively, so that when the bipolar plate memberis assembled into the fuel cell stack, the third and fourth pocketmembers are secured at their respective positions relative to the platemember using pressure in the fuel cell stack.

In certain embodiments, the plate member comprises a planar central areadisposed between the first and second end segments, and each of thefirst and second end segments includes: a first portion co-planar with,and extending from, the central area, a second portion following thefirst portion and extending transverse to the first portion outwardlyfrom the first surface of the first portion, and a third portionfollowing the second portion and extending transverse to the secondportion in a direction away from, and substantially parallel to, thefirst portion. In such embodiments, the first and second portion of thefirst end segment form the first portion of the first pocket member, andthe first and second portions of the second end segment form the firstportion of the second pocket member. Moreover, in such embodiments, thesecond portion of each of the first and second pocket members is formedby an anode wet seal member which is releasably secured to the platemember, wherein the anode wet seal member includes first and second legsintegrally connected to one another, with the second leg being parallelto the first leg and being shorter than the first leg. When the anodewet seal member is releasably secured to the respective first or secondsegment of the plate member, one part of the first leg forms the secondportion of the respective first or second pocket member and another partof the first leg extends along the third portion of the respective firstor second end segment, and the second leg of the anode wet seal memberis hemmed around the third portion of the respective first or second endsegment and abuts the second surface of the third portion of therespective first or second end segment. Each anode wet seal member alsoincludes first and second extensions at opposing sides of the first legand extending from the one part of the first leg that forms the secondportion of the pocket, so that when the anode wet seal member is securedto the plate member, the first and second extensions are folded towardthe first portion of the respective first or second end segment of theplate member to form end walls of the pocket.

Each of the third and fourth pockets is formed by a cathode wet sealmember which is separate from the plate member and which abuts therespective third or fourth end segment of the plate member. Each cathodewe seal member includes a bottom wall abutting the respective third orfourth end segment, a top wall opposing the bottom wall, and an outersidewall connecting the top and bottom walls and opposing end walls. Inaddition, each cathode wet seal member includes a main portion and firstand second corners extending from opposing ends of the main portion toform opposing corners of the respective third or fourth pocket. The mainportion includes the bottom wall of the respective third or fourthpocket and central portions of the top wall and the outer sidewall ofthe respective third or fourth pocket. Each of the first and secondcorners of the cathode wet seal member includes an end wall and endportions of the top wall and the outer sidewall of the respective thirdor fourth pocket, wherein the end wall and the end portion of the outersidewall extend beyond the height of the central portion of the outersidewall and at least up to the third portion of the respective first orsecond end segment of the plate member.

In certain embodiments, the plate member includes two S-shapedprotrusions protruding outwardly from an outer edge of the third endsegment and aligned with the first and second end segments of the platemember so that a central portion of each S-shaped protrusion isco-extensive with the second portion of the first or second end segment.Similarly, the plate member may include two S-shaped protrusionsprotruding outwardly from an end of the fourth end segment and alignedwith the first and second end segments of the plate member so that thecentral portion of each S-shaped protrusion is co-extensive with thesecond portion of the respective first or second end segment. Inaddition, each corner of the cathode wet seal member forming the thirdor fourth pocket may include an S-shaped notch in the end portion of itsouter sidewall to allow a corresponding S-shaped protrusion to passtherethrough. In other embodiments, the shape of the protrusions isvaried, so that for example, in some embodiments, the protrusion onlyincludes the central portion co-extensive with the second portion of therespective first and second segment. In such embodiments, notches in thecathode wet seal member corresponding in shape and position to theprotrusions may be included, or may be omitted.

A fuel cell stack assembly which includes the bipolar separator assemblydescribed above is also described. Moreover, an assembly and a method offorming the assembly that includes an anode-side sub-assembly and acathode-side sub-assembly are also described. In such assembly, theanode-side sub-assembly includes the plate member having first andsecond opposing surfaces compatible with furl and oxidant gases,respectively, first and second opposing end segments and third andfourth opposing segments transverse to the first and second opposing endsegments, an anode current collector abutting the first surface of theplate member, and first and second anode wet seal members formedseparately from the plate member and releasably secured to the platemember so as to form first and second pockets on the first surface ofthe plate member adjacent the first and second opposing end segmentswith the first and second pockets enclosing opposing ends of the anodecurrent collector. The cathode-side sub-assembly comprises first andsecond cathode wet seal members formed separately from the plate memberof the anode-side subassembly and adapted to form third and fourthpockets on the second surface of the plate member and to be releasablypositioned adjacent the third and fourth opposing end segments, and acathode current collector cooperating with the first and second cathodewet seal members so that the third and fourth pocket members encloseopposing ends of the cathode current collector. In forming the assembly,the cathode-side sub-assembly is assembled with the anode-sidesub-assembly so that the cathode-side sub-assembly abuts the secondsurface of the plate member of the anode-side sub-assembly and the firstand second cathode wet-seal members form the third and fourth pocketsadjacent the second surface of the plate member. The method of formingthe assembly may be automated.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and aspects of the present invention willbecome more apparent upon reading the following detailed description inconjunction with the accompanying drawings, in which:

FIG. 1 shows a corner of a bipolar separator assembly of the presentinvention;

FIG. 2 shows a close up view of the bipolar separator assembly corner ofFIG. 1;

FIG. 3A shows a corner portion of an anode wet seal pocket portion andplate member of the bipolar separator assembly of FIG. 1;

FIG. 3B shows a cross-sectional view of an anode wet seal pocket portionand plate member of the bipolar separator assembly corner of FIG. 1;

FIG. 4 shows a corner portion of a cathode wet seal pocket portion ofthe bipolar separator assembly of FIG. 1;

FIG. 5 shows a cross-section of the corner portion of a cathode wet sealpocket portion of FIG. 4;

FIG. 6 shows another embodiment of the corner portion of the cathode wetseal pocket portion of the bipolar separator assembly of FIG. 1;

FIG. 7 shows a cross-section of the corner portion of a cathode wet sealpocket portion of FIG. 6;

FIGS. 8A-8D show the assembly process for assembling the bipolarseparator assembly of FIG. 1.

DETAILED DESCRIPTION

FIGS. 1-4 show portions of the bipolar separator assembly 100 of thepresent invention which includes a separator plate member 102 and aplurality of wet seal pocket members 104 which are either formedseparately from the separator plate member 102 or portions of which areformed separately from the separator plate member 102. As discussedherein below, the wet seal pocket members 104, or portions thereof areattached to, or coupled with, the separator plate member 102 without theneed to use welding, or with only limited use of welding. In addition,each wet seal pocket member 104 is configured so that an end of acurrent collector can be inserted into the wet seal pocket. Moreover, asdiscussed in more detail below, the bipolar separator assembly 100provides additional sealing in the corner areas of the assembly and usesthe pressure of manifold sealing gaskets for further sealing between thefuel and oxidant sides in the corner areas of the stack.

FIG. 1 shows a corner portion of the bipolar separator assembly 100 ofthe present invention with current collectors and electrodes abuttingthe bipolar separator assembly. In particular, the bipolar separatorassembly 100 includes first and second opposing surfaces 100 a, 100 b,compatible with an anode side of a first fuel cell and a cathode side ofa second fuel cell, respectively. As shown in FIG. 1, an anode currentcollector 150 abuts the first surface 100 a of the bipolar separatorassembly and an anode electrode 155 abuts the anode current collector150. Similarly, a cathode current collector 160 abuts the second surface100 b of the bipolar separator assembly and a cathode electrode 165abuts the cathode current collector 160.

As shown and discussed in more detail below, the bipolar separatorassembly 100 includes the separator plate member 102 having the opposingfirst and second surfaces 100 a, 100 b, which are compatible with fueland oxidant gases, respectively, and a plurality of wet seal pocketmembers 104, at least a portion of each pocket member being formedseparately from the plate member 102 and attached or coupled to theplate member 102. The separator plate member 102 of the presentillustrative embodiment has a substantially rectangular shape andincludes first and second opposing end sections 102 a, 102 b (endsection 102 b is not visible in FIG. 1) and opposing end sections 102 c,102 d (end section 102 d is not visible in FIG. 1) transverse to theopposing end sections 102 a, 102 b. Adjacent each of the end sections,the plate member 102 includes a wet seal pocket member 104. Inparticular, wet seal pocket members 104 a, 104 b are situated adjacentopposing end sections 102 a, 102 b of the plate member 102 so as to formpockets on the first surface 100 a of the plate member. Wet seal pocketmembers 104 c, 104 d are situated adjacent opposing end sections 102 c,102 d of the plate member 102 so as to form pockets on the secondsurface 100 b of the plate member. As will be discussed in more detailbelow, the wet seal pocket members 104 a-d, or portions thereof, areformed separately from the plate member 102 and are attached to theplate member 102 either without welding or using only limited welding.The pocket members 104 a-d form wet seal regions of the fuel cell stack,while the central area of the bipolar separator assembly 100 between thepocket members forms the active area of the fuel cell stack.

As shown in FIG. 1, the anode current collector 150 abuts the firstsurface 100 a of the separator plate member 102, with opposing endportions of the anode current collector 150 extending into, and beinghoused underneath, the wet seal pocket members 104 a, 104 b. The anodeelectrode 155 abutting the anode current collector 150 is disposed inthe central area of the bipolar separator assembly 100. The cathodecurrent collector 160 abuts the second surface 100 b of the separatorplate member 102 with opposing end portions of the cathode currentcollector 160 extending into, and being housed underneath, the wet sealpocket member 104 c, 104 d. The cathode electrode 165 abutting thecathode current collector 160 is disposed in the central area of thebipolar separator assembly 100. In the illustrative embodiment shown inFIG. 1, the anode and cathode current collectors 150, 160 are corrugatedcurrent collectors, with the corrugations of the current collectorsforming flow channels for the reaction gases.

FIG. 2 shows a more detailed view of the assembled corner of the bipolarseparator assembly 100 of FIG. 1, without the cathode and anodeelectrodes. The separator plate member 102 of the separator assemblyseparates the fuel gas from the cathode gas and each surface 100 a, 100b of the plate member includes the central area and two opposing endsections 102 a-b or 102 c-d. In the embodiment of FIGS. 1-4, theseparator plate member 102 has a substantially planar central area 103a, corresponding to the central area of the anode side surface 100 a,and S-shaped end portions at opposing ends forming each of the endsections 102 a-b. In particular, each end section 102 a, 102 b of theseparator plate member 102, adjacent to which the pocket member 104 a,104 b is situated, has the substantially S-shaped cross-section, andincludes a first portion 103 b extending from the planar central area103 a and co-planar with the central area 103 a. The first portion 103 bis followed by a second portion 103 c transverse to the first portion103 b and formed by bending the separator plate member in the directionof the anode side 100 a of the bipolar separator assembly. The secondportion 103 c is then followed by a third portion 103 d transverse tothe second portion 103 c and formed by bending the separator platemember outwardly. In the embodiment shown, the second portion 103 c ofthe end section 102 a is substantially perpendicular to the first andthird portions 103 b, 103 d, and the third portion 103 d extends in aplane that is parallel to the plane of the first portion 103 b. In thisway, the first, second and third portions 103 b-d of each end section102 a, 102 b form a step in the separator plate member 102.

As shown in FIG. 2, the first portion 103 b of the end section 102 aforms an upper wall of the pocket member 104 a and the second portion103 c of the end section 102 a forms a sidewall of the pocket member 104a. The remaining portions of the pocket member 104 a are formedseparately from the plate member 102, as shown in FIG. 3 and are coupledto the plate member without use of welding or with only limited use ofwelding. Although not shown, the pocket member 104 b is formed similarlyto the pocket member 104 a, so that the first and second portions 103 b,103 c of the end section 102 b form the upper wall and a sidewall,respectively, of the pocket member 104 b and the remaining portions ofthe pocket member 104 b are formed separately from the plate member 102and thereafter coupled to the plate member.

The S-shaped end sections 102 a, 102 b of the plate member 102 extendacross the entire width of the plate from an edge of the end section 102c to an opposing edge of the end section 102 d. As a result, the endsection 102 c of the plate member overlaps with the end section 102 a ata corner A of the plate member, and the end section 102 d overlaps withthe end section 102 a at a second corner B (not shown in FIG. 2) of theplate member. Similarly, the end section 102 c overlaps with the endsection 102 b at a third corner C (not shown in FIG. 2), which isopposite the corner A and diagonal from the second corner B, and the endsection 102 d overlaps with the end section 102 b at a fourth corner D(not shown in FIG. 2) which is opposite the corner B and diagonal fromthe third corner A. The configuration of the plate member 102, and inparticular, the folds in the plate member forming the S-shaped endsections 102 a, 102 b prevent the fuel gas flowing along the anode sideof the fuel cell from reaching the corner of the fuel cell stack. Inthis way, even if the corners of the fuel cell stack are notsufficiently sealed off, the fuel gas is prevented from diffusingthrough the corners and is sealed from the oxidant gas flowing throughthe cathode side of the fuel cell because the plate member configurationdoes not allow the fuel to reach the corners of the fuel cell stack.

As shown in FIG. 2, the pocket member 104 c is formed separately fromthe plate member 102 on the cathode side 100 b of the plate member andcoupled with the plate member adjacent the end section 102 c. Althoughnot shown, the pocket member 104 d is formed in a similar manner to thepocket member 104 c adjacent the end section 102 d of the plate member.

As shown in FIG. 2, the plate member 102 includes an S-shaped protrusion112 extending from an outer edge of the end section 102 c at thelocation of the S-shaped bend in the end section 102 a. The S-shapedprotrusion extends from, and follows along, at least a part of the firstportion 103 b, the second portion 103 c and at least a part of the thirdportion 103 d of the S-shaped end section 102 a. Although not shown, theplate member 102 also includes a similar S-shaped protrusion extendingfrom the outer edge of the end segment 102 c at the location of theS-shaped bend in the end segment 102 b and may include further S-shapedprotrusions extending from an outer edge of the end segment 102 d at thelocations of the S-shaped bends in the end segments 102 a and 102 b. Theconfigurations of the S-shaped protrusions are substantially the same asthe S-shaped protrusion 112 shown in FIG. 2. In the embodiment shown inFIG. 2, the S-shaped protrusion 112 protrudes from the edge of the plateby a predetermined amount so as to prevent collapse of the manifoldsealing gasket, as described in more detail below. In FIG. 2, brokenlines are used to show the positioning and width of the manifold sealinggasket that would abut the face of the fuel cell stack after the bipolarseparator assembly 100 is assembled into the stack. As shown, the endsection 102 a of the plate member is configured so that the S-shapedportion of the end section 102 a, and the corresponding S-shapedprotrusion 112 are located in the middle of the width of the manifoldsealing gasket when the bipolar separator assembly 100 is assembled intothe stack and the manifold sealing gasket is pressed against the stackface. In this way, when the manifold sealing gasket abuts the fuel cellsstack face, the edge of the S-shaped portion of the end section 102 apresses into the gasket, thus making an effective seal between thecathode oxidant and anode fuel gases. Moreover, the S-shaped protrusion112 protrudes into the manifold sealing gasket and acts to stop themanifold sealing gasket from collapsing.

In conventional fuel cells, collapse of the manifold sealing gasket canlead to premature failure of the fuel cell stack due to gas leakage.However, the S-shaped protrusions 112 of the bipolar separatorassemblies of the present invention prevent gas leakage and collapsingof the manifold sealing gasket. Specifically, when the manifold sealinggasket is pressed against the fuel cell stack face, the manifold gasketis allowed to only collapse until the S-shaped protrusion hits a soliddielectric member behind the gasket, thereby transferring the load fromthe gasket to the dielectric member and preventing further collapse ofthe gasket. In this way, gas leaks between the cathode and anode sidesare prevented.

Although in the embodiment shown in FIG. 2, the protrusions have an Sshape, it is understood that in other embodiments, the shape of theprotrusions may be varied. For example, in some embodiments, theprotrusion is linear and only includes the central portion that extendsfrom and follows along the second portion 103 c of the respective endsection. The linear configuration of the protrusions would achievesimilar gas sealing between the cathode and anode sides and wouldprevent gasket collapse during operation as the S-shaped protrusionsdescribed above.

FIG. 2 shows the bipolar separator assembly 100 in its assembled state,with the pocket members 104 c-d, or portions of the pocket members 104a-b, coupled to separator plate member 102 adjacent the respective endsections 102 c-d and 102 a-b, and with the anode and cathode currentcollectors disposed adjacent the anode and cathode surfaces 100 a, 100 bof the separator plate member 102. FIGS. 3A and 3B show, in more detail,the coupling and sealing between the portions of the pocket member 104a-b with the separator plate member 102. In particular, FIG. 3A shows apartially assembled bipolar separator assembly 100, which includes acorner portion of the plate member 102, the first pocket member 104 aand the anode current collector, but does not include the third pocketmember 104 c coupled to the plate member 102. FIG. 3B shows a portion ofa cross-section of the partially assembled bipolar separator assembly100 of FIG. 3A.

As shown in FIGS. 3A and 3B, the S-shaped end section 102 a of the platemember forms a portion of the first pocket member 104 a, wherein thesecond portion 103 c of the S-shaped end section 102 a forms a sidewallof the first pocket member 104 a that extends along the length of theend section 102 a. The upper wall of the pocket member 104 a is alsoformed by the end section 102 a of the plate member, and in particular,by the first portion 103 b, or at least a part of the first portion 103b, of the end section 102 a. As also shown, the remaining portion of thepocket member 104 a is formed by an anode wet seal member 106, which isformed separately from the plate member 102. The anode wet seal member106 forms a lower wall 104 a 1 of the first pocket member 104 a andcouples the lower wall 104 a 1 to the end section 102 a of the platemember.

As shown in FIGS. 3A-B, the anode wet seal member 106 comprises aU-shaped member which includes a first leg 106 a and a second leg 106 bparallel to the first leg 106 a and integrally coupled to the first leg106 a by a U-shaped connecting portion 106 c. As shown in FIG. 3B, thesecond leg 106 b of the anode wet seal member 106 a is shorter than thefirst leg 106 a. In coupling the anode wet seal member 106 to the platemember 102, the first leg 106 a extends along and adjacent the thirdportion 103 d of the end section 102 a and thereafter parallel to thefirst portion 103 b of the end section 102 a on the anode side surface100 a of the plate member 102. The part of the first leg 106 a extendingalong the first portion 103 b forms the lower wall 104 a 1 of the firstpocket member 104 a. The second leg 106 b, together with the U-shapedconnecting portion 106 c, is hemmed around the outer periphery of thethird portion 103 d of the end section 102 a and extends along at leasta part of the third portion 103 d on the cathode side surface 100 b ofthe plate member 102, thus creating a hemmed area. With thisconstruction, the first leg 106 a forms the anode wet seal pocket 104 a,while the connecting portion 106 c and the second leg 106 b form theseal between the fuel gas and the oxidant gas. In particular, whenmultiple fuel cells are stacked to form a fuel cell stack with thebipolar separator assemblies 100 of the present invention disposedbetween adjacent fuel cells, the stack pressure is used to seal the gasbetween the wet seals formed by the pocket members and the electrolytematrix of the fuel cell. In addition, the stack pressure also acts toseal between the separator plate member 102 and the anode wet sealmember 106 in the hemmed area.

Although in FIGS. 3A and 3B, the anode wet seal member 106 is coupledwith the separator plate member 102 without using any welding, incertain embodiments, the seal in the hemmed area of the wet seal member106 may be strengthened by a laser lap-weld so as to permanently jointhe anode wet seal member 106 to the separator plate member 102. Thelaser lap-weld may be formed anywhere in the hemmed area of the anodewet seal member 106 and may extend the entire length of the bipolarplate assembly 100.

As shown in FIGS. 3A-3B, the end of the anode current collector 150 isinserted into the pocket member 104 a created by the first end section102 a and the wet seal member 106. The anode current collector 150 stopsat the second portion 103 c of the first end section 102 a. Each of theS-shaped end sections 102 a, 102 b creates a discontinuity, or a shearplane, in the middle of the wet seal region of the fuel cell, with thesecond portion 103 c separating the anode current collector from furthercorrugations in the hemmed area of the fuel cell. The shear plane isbridged by the wet seal itself, rather than by the matrix, and thusprotecting the matrix from shearing forces and from cracking.

Referring to FIGS. 2 and 3A, the wet seal member 106 also includes endwall portions 106 d extending from opposing side ends of the first leg106 a. When the wet seal member 106 is coupled with the first endsection 102 a, each end wall portion 106 d is folded upwardly so as tocover the openings at opposing ends of the first end section and to formopposing end walls of the pocket member 104 a. As shown in FIGS. 2 and3A, the end walls 106 d of the pocket member 104 a are shaped so as toextend from the lower wall 104 a 1 of the pocket member 104 a up to thefirst portion 103 b of the end section 102 a forming the upper wall ofthe pocket member 104 a, without covering the S-shaped protrusion.Although not shown in FIGS. 2 and 3A-3B, the pocket member 104 b has asubstantially the same construction as the pocket member 104 a, andincludes a like U-shaped wet seal member coupled to the second endsection 102 b. The U-shaped wet seal member of the second pocket member104 b has a similar construction and coupling mechanism as the wet sealmember 106 of the first pocket member, and also includes end wallportions that form opposing end walls of the pocket member 104 b.

FIG. 4 shows a first embodiment of a cathode sub-assembly of the bipolarseparator assembly 100 of FIGS. 1 and 2, which includes a cathode wetseal member 108 forming the third pocket member 104 c and the cathodecurrent collector 160 held by the cathode wet seal member 108. Inaddition, FIG. 5 shows a cross-section of the cathode sub-assembly ofFIG. 4 along a line indicated as “Cross-Section” in FIG. 4. As shown inFIGS. 4 and 5, the cathode wet seal member 108 includes a U-shapedchannel 109, which forms an inner portion of the third pocket member 104c, and an outer wet seal 110 disposed on top of, or at least partiallyaround, the U-shaped channel 109.

As shown in FIGS. 4 and 5, the U-shaped channel 109 includes a first legor flange 109 a and a second leg or flange 109 b which is connected tothe first leg 109 a by a connecting portion 109 c and which issubstantially parallel to the first leg 109 a. In the embodiment shownin FIG. 5, the first leg 109 a is shorter than the second leg 109 b, butin other embodiments, the first and second legs 109 a, 109 b may havethe same length or the first leg 109 a may be longer than the second leg109 b.

The outer wet seal 110 of this embodiment includes a main wall 110 a,forming a top wall of the third pocket member 104 c opposing the platemember 102, a sidewall 110 b and end walls 110 c. As shown in FIG. 4,the outer wet seal 110 forms a main or central portion and two cornerportions 111 of the third pocket member 104 c at the ends thereof. Thecorner portions 111 are formed by the end walls 110 c and end portionsof the sidewall 110 b, wherein the height of the end walls 110 c and ofthe end portions of the sidewall 110 b is greater than the height of thecentral portion of the sidewall 110 b.

In assembling the cathode wet seal member 108, the outer wet seal 110 isplaced on top of the U-shaped channel 109 so that the main wall 110 a ofthe outer wet seal abuts the first leg 109 a of the U-shaped channel andthe sidewall 110 b of the outer wet seal 110 abuts the connectingportion 109 c of the U-shaped channel 109. To assemble the cathode wetseal member 108 with the cathode current collector 160 to form thecathode sub-assembly, an end of the cathode current collector 160 isinserted into the cathode wet seal member 108 and in particular, intothe U-shaped channel 109, so that the inner surfaces of the first andsecond legs 109 a, 109 b of the U-shaped channel 109 abut opposingsurfaces of the cathode current collector 160.

When the cathode sub-assembly is assembled into the separator assemblyand the separator assembly is assembled into the fuel cell stack, theouter surface of the second leg 109 b of the U-shaped channel abuts thethird end section 102 c of the plate member 102, and the main wall 110 aof the outer wet seal 110 contacts the electrolyte matrix of the fuelcell. The stack pressure is used for sealing between the outer wet seal110 and the electrolyte matrix and for sealing between the U-shapedchannel 109 and the separator plate member 102. Referring to FIG. 2,which shows the separator assembly in an assembled state, the end wall110 c and the end portion of the sidewall 110 b extends so as to atleast cover or enclose the third portion 103 d of the separator platemember end section coupled with the anode wet seal member 106. Inaddition, the end portion of the sidewall 110 b is also shaped toconform to the shape of the separator plate end section 102 a, and inparticular, the end portion of the sidewall 110 b includes anindentation 110 b 1 therein so as to expose the S-shaped protrusion 112and to allow the S-shaped protrusion 112 to protrude from the surface ofthe separator assembly. As mentioned above, in certain embodiments, theprotrusion 112 is a linear protrusion instead of an S-shaped protrusion,and in such embodiments, the end portion of the sidewall 110 b is sizedand/or shaped so as to allow the linear protrusion to protrude from thesurface of the separator assembly.

Although FIGS. 4 and 5 only show one corner of the cathode wet sealmember 108, it is understood that the configuration of the other cornerof the cathode wet seal member forming the third pocket member 104 c issimilar to the configuration of the corner shown in FIGS. 4 and 5. Inaddition, the configuration of the cathode wet seal member forming thefourth pocket member is substantially the same as the configuration ofthe wet seal member 108 shown in FIGS. 4 and 5. The cathode wet sealmembers forming the third and fourth pocket members 104 c, 104 d areformed separately from the separator plate member 102, and in theembodiment shown in FIGS. 4 and 5, the cathode wet seal members are notpermanently coupled to the separator plate and do not require the use ofwelding. Moreover, the corners of the cathode wet seal members in FIGS.4 and 5 are flat, which is critical for sealing the fuel cell stack tothe manifold. As a result, the separator assembly provides for improvedsealing of the manifold sealing gaskets to the fuel cell stack andimproved sealing between the fuel and oxidant gases in the corners ofthe stack.

In the embodiment shown in FIGS. 4 and 5, the cathode sub-assembly 108is formed from two separate pieces, namely, the U-shaped channel 109 andthe outer wet seal 110, which may be formed from the same material orfrom different materials. In certain embodiments, the U-shaped channel109 and the outer wet seal 110 are formed from one or more metallicmaterials. However, in other embodiments, the cathode sub-assembly 108may be formed from a single integral piece or from two pieces which areconnected by suitable means to form one a piece cathode sub-assembly.

FIG. 6 shows another embodiment of a cathode sub-assembly of the bipolarseparator assembly 100 of FIGS. 1 and 2 with the cathode sub-assemblybeing formed as a single integral piece. As in the embodiment of FIGS. 4and 5, the cathode sub-assembly of this embodiment includes a cathodewet seal member 108 forming the third pocket member 104 c and thecathode current collector 160 held by the cathode wet seal member 108.In addition, FIG. 7 shows a cross-section of the cathode sub-assembly ofFIG. 6 taken along a line indicated as “Cross-section” in FIG. 6. Asshown in FIGS. 6 and 7, the cathode wet seal member 108 includes aU-shaped main portion 113 that forms the third pocket member 104 c andcorner portions 114 that form opposing corners of the pocket member 104c. In the embodiment shown in FIG. 6, the main portion 113 and thecorner portions 114 of the cathode wet seal member 108 are integrallyformed, preferably from the same piece of metallic material. However, inother embodiments, the corner portions 114 may be attached to the mainportion 113 by a suitable means, such as welding or the like. Theconstruction of the main portion 113 of the cathode wet seal member 108and its attachment to the separator plate member 102 is shown in moredetail in FIG. 7.

As shown in FIGS. 6 and 7, the main portion 113 comprises asubstantially U-shaped member, including a first leg or flange 113 a anda second leg or flange 113 b which is connected to the first leg 113 aby a connecting portion 113 c and which is substantially parallel to thefirst leg 113 a. In the embodiment shown in FIG. 6, the first leg 113 ais shorter than the second leg 113 b, but in other embodiments, thefirst and second legs 113 a, 113 b may have the same length or the firstleg may be longer than the first. The first and second legs 113 a, 113 bform opposing upper and lower walls of the third pocket member, whilethe connecting portion 113 c forms the sidewall of the third pocketmember 104 c connecting the upper and lower walls. As shown in FIG. 7,the cathode current collector 160 is inserted into the third pocket 104c, and in particular, into the space between the first and second legs113 a, 113 b of the cathode wet seal 113. When the separator assembly isassembled into the fuel cell stack, the first leg 113 a contacts theelectrolyte matrix of the fuel cell while the second leg 113 b contactsthe third end segment 102 c of the separator plate member 102 a. Stackpressure is used for sealing between the wet seals and the electrolytematrix and for sealing between the cathode wet seal 113 and theseparator plate member 102.

Referring now back to FIG. 6, the corner portion 114 extending from themain portion 113 is shown and forms the corner of the third pocketmember 104 c. The corner portion 114 is integral with the main portion,and includes a first wall 114 a extending from the first leg 113 a ofthe main portion 113 so as to form the corner of the upper wall of thepocket member 104 c and first and second flanges or extensions 114 b and114 c extending from the first wall 114 a. The first flange 114 b issubstantially perpendicular to the first wall 114 a and is integral withthe connecting portion 113 c of the main portion 113, forming the cornersidewall portion of the third pocket 104 c. The second flange 114 c issubstantially perpendicular to the first wall 114 a and to the firstflange 114 b, and forms an end wall of the third pocket 104 c. If thecathode wet seal member 108 of FIGS. 6 and 7 is used in the separator ofFIG. 2, the first and second flanges 114 b, 114 c extend beyond theheight of the connecting portion 113 c, and cover or enclose the entireheight of the separator assembly corner. Referring to FIG. 2, the firstand second flanges 114 b, 114 c of the wet seal member 108 extend so asto at least cover or enclose the third portion 103 d of the separatorplate member end section 102 a coupled with the anode wet seal member106. As shown in FIG. 2, the first flange 114 b is also shaped toconform to the shape of the separator plate end section 102 a, and inparticular the first flange 114 b includes an indentation 114 b 1therein so as to expose the S-shaped protrusion 112 and to allow theS-shaped protrusion 112 to protrude from the surface of the separatorassembly. As described above, in some embodiments, the protrusions fromthe end sections of the plate may have a linear shape, instead of theS-shape. In such embodiments, the first flange 114 b may include anindentations corresponding to the linear shape and position of thelinear protrusion. Alternatively, the first flange 114 b may beconfigured so that no indentation is required for exposing the linearprotrusion. It is understood that the flanges at the other ends of theassembly have similar configurations as the first flange 114 b.

When the separator assembly is assembled into the fuel cell stack, oneside of the first wall 114 a of the corner portion 114, along with thefirst leg 113 a of the main portion 113, contacts the electrolyte matrixof the fuel cell, while the other side of the first wall 114 a contactsthe cathode current collector 160 inserted into the pocket member 104 c.As shown in FIG. 6, the corner portion 114 does not include a wallcoextensive with the second leg 113 b and the lower surface of thecathode current collector, which is not in contact with the first wall114 a, is open in the subassembly of FIG. 6, and faces the separatorplate member 102 hemmed with the second leg 106 b of the anode wet sealmember 106.

Although FIGS. 6 and 7 only show one corner portion 114 of the cathodewet seal member 108, the configuration of the other corner portion ofthe cathode wet seal member forming the third pocket member 104 c issimilar to the configuration of the corner portion 114 of FIGS. 6 and 7.In addition, the configuration of the cathode wet seal member formingthe fourth pocket member is substantially the same as the configurationof the wet seal member 108 shown in FIGS. 6 and 7. As in the embodimentof FIGS. 4 and 5, the cathode wet seal members of FIGS. 6 and 7 areformed separately from the separator plate member 102 and in theembodiment shown in FIGS. 6 and 7, the cathode wet seal members are notpermanently coupled to the separator plate member 102 and do not requirethe use of welding. Also as in the embodiment of FIGS. 4 and 5, thecorner portions of the cathode wet seal members of FIG. 6 form cornersthat are as flat as possible, which is critical for sealing the fuelcell stack to the manifold. Therefore, the separator assembly providesfor improved sealing of the manifold sealing gaskets to the fuel cellstack and improved sealing between the fuel and oxidant gases in thecorners of the stack.

The manufacturing method of the separator assembly of FIGS. 1-7 may beautomated. In addition, the manufacturing method of the separatorassembly of FIGS. 1-7 allows for placement or positioning of thecorrugated current collectors adjacent opposing sides of the separatorplate member before, or simultaneously with, attachment or coupling ofthe wet seal members to the plate member. In this way, the bending andmanipulating of the corrugated current collectors to insert them intothe wet seal members is avoided. FIGS. 8A-8D illustrate themanufacturing and/or assembling process for manufacturing the separatorassembly of FIGS. 1-7. Although FIGS. 8A-8D only show a corner portionof the separator assembly of FIGS. 1-7, it is understood that theconstructions of the ends of the assembly that are not shown in FIGS.8A-8D are similar to those shown in FIGS. 8A-8D.

As shown in FIG. 8A, the first step of manufacturing the separatorassembly includes providing an anode current collector 150, such as acorrugated anode current collector. In the first step, the anode currentcollector may be positioned in a predetermined location and with apredetermined orientation so as to be properly aligned with the othercomponents of the separator assembly during the manufacturing process.

In the second step, shown in FIG. 8B, the separator plate member 102 isprovided and placed on top of the anode current collector 150. As shown,in FIG. 8B, the separator plate member 102 is positioned so that theanode side surface 100 a of the plate member 102 faces the anode currentcollector 150 and so that the anode current collector 150 fits withinthe space formed between the second portions 103 c of the plate memberend sections 102 a, 102 b.

In the third step, shown in FIG. 8C, the anode wet seal member 106 isprovided and secured or coupled to the separator plate member 102 by ahemming operation. As described above with respect to FIG. 3, the anodewet seal member 106 includes the first and second legs 106 a, 106 bconnected by the connecting portion 106 c, forming the U-shaped member.In addition, the anode wet seal member 106 includes end wall portions106 d provided at opposing ends of the first leg 106 a and adapted tocover the openings at opposing ends of the first end section 102 a. Inthe third step of FIG. 8C, the hemming operation is performed by slidingthe anode wet seal member 106 onto the third portion 103 d of therespective end section 102 a, 102 b of the plate member 102 so that thefirst leg 106 a of the anode wet seal member 106 extends under the endsection 102 a or 102 b and the second leg 106 b is hemmed over the thirdportion 103 d of the end section 102 a, 102 b.

In some embodiments, the anode wet seal member 106 provided in the thirdstep may be in a substantially planar, unhemmed form so that the firstand second legs 106 a, 106 b and the end wall portions 106 d arecoplanar with respect to one another. In such embodiments, each unhemmedanode wet seal member 106 is aligned with respect to the respective endsection 102 a, 102 b of the plate member, so that the end wall portions106 d of the wet seal member 106 are properly aligned with therespective end openings formed by the first and second portions 103 b,103 c of the plate member end section 102 a, 102 b. During hemmingoperation of this embodiment, the second leg 106 b of the wet sealmember 106 is then folded over respective end section 102 a, 102 b sothat the wet seal member 106 at least partially encloses the thirdportion 103 d of the end section. Similarly, the end wall portions 106 dof each wet seal member 106 are folded upwardly so as to cover theopenings at opposing ends of the first end section 102 a. The resultinganode wet seal member 106 coupled with the plate member 102 and forminga pocket member 104 a is shown in FIG. 8C.

Finally, in the fourth step shown in FIG. 8D, the cathode subassembly ofFIG. 4 or of FIG. 6 is provided and assembled with the anode subassemblyshown in FIG. 8C. As described herein above, the cathode subassemblyincludes the cathode current collector 160 and cathode wet seal members108 forming pocket members 104 c, 104 d, with opposing ends of thecathode current collector 160 being inserted into the pocket members 104c, 104 d formed by two cathode wet seal members 108. In the fourth step,the cathode subassembly is positioned adjacent the cathode surface 100of the plate member 102 so that the third and fourth pocket members 104c, 104 d formed by the cathode wet seal members 108 are aligned with thethird and fourth end sections 102 c, 102 d of the plate member 102.

The manufacturing and/or assembly process shown in FIGS. 8A-8D may beautomated so as to reduce the manufacturing time and costs and toincrease production rates for separator assemblies of the presentinvention. In addition, the method of FIGS. 8A-8D allows the cathode andanode current collectors to be placed prior to assembly of the pocketmembers with the separator plate, thus eliminating manual manipulationand the requirements for bending of the current collectors or for usingseveral separate pieces to form each current collector. In automatingthe manufacturing process of FIGS. 8A-8D, suitable manufacturingassembly including equipment known in the art may be used forsupporting, positioning and assembling the components of the separatorassemblies. In addition, the manufacturing assembly may include acontroller which controls the formation of the anode-side sub-assembly,as shown in FIGS. 8A-8B, controls the formation of the cathode-sidesub-assembly shown in FIG. 8C and controls the assembly of theanode-side and cathode-side sub-assemblies to form the separatorassembly.

In all cases it is understood that the above-described arrangements aremerely illustrative of the many possible specific embodiments whichrepresent applications of the present invention. Numerous and variedother arrangements can be readily devised in accordance with theprinciples of the present invention without departing from the spiritand the scope of the invention.

We claim:
 1. A bipolar separator assembly for use with a fuel cellcomprising: a plate member having opposing first and second surfacescompatible with fuel gas and oxidant gas, respectively, the plate memberhaving first and second opposing end segments and third and fourthopposing end segments which are transverse to the first and secondopposing end segments; first and second pockets situated adjacent thefirst and second end segments and extending outward of the firstsurface, the first and second pockets being configured to allow opposingends of an anode current collector to be inserted into the respectivefirst and second pockets so as to enclose the opposing ends of the anodecurrent collector; and third and fourth pockets situated adjacent saidthird and fourth end segments and extending outward of said secondsurface, said third and fourth pockets being configured to allowopposing ends of a cathode current collector to be inserted into therespective third and fourth pockets so as to enclose the opposing endsof the cathode current collector; wherein the first end segment of theplate member forms a first portion of the first pocket and the secondend segment of the plate member forms a first portion of the secondpocket; wherein a second portion of the first pocket is formedseparately from the plate member and is releasably secured to the firstend segment of the plate member by being hemmed around a portion of thefirst end segment; and wherein a second portion of the second pocket isformed separately from the plate member and is releasably secured to thesecond end segment of the plate member by being hemmed around a portionof the second end segment.
 2. A bipolar separator assembly in accordancewith claim 1, wherein: the third and fourth pockets are formedseparately from the plate member and releasably positioned adjacent thethird and fourth end segments of the plate member, respectively, andwhen the bipolar separator plate is assembled into the fuel cell stack,the third and fourth pockets are secured at their respective positionsrelative to the plate member using pressure in the fuel cell stack.
 3. Abipolar separator assembly in accordance with claim 2, wherein: each ofthe third and fourth pockets is formed by a cathode wet seal memberseparate from the plate member and abutting the respective third orfourth end segment of the plate member; and each cathode wet seal memberincludes a U-shaped channel member and an outer wet seal, the U-shapedchannel member having a bottom wall abutting the respective third orfourth end segment, a top wall opposing the bottom wall, and a sidewallconnecting the top and bottom walls, and the outer wet seal positionedrelative to the U-shaped channel member so as to partially enclose theU-shaped channel member and having a top wall abutting the top wall ofthe U-shaped channel member, a sidewall abutting the sidewall of theU-shaped channel member and opposing end walls.
 4. A bipolar separatorassembly in accordance with claim 1, wherein said plate member includesfirst and second protrusions protruding from an outer periphery of thethird end segment and third and fourth protrusions protruding from anouter periphery of the fourth end segment, and wherein each of saidfirst, second, third and fourth protrusions is positioned so as toprotrude into a manifold sealing gasket when the bipolar separatorassembly is assembled into the fuel cell stack.
 5. A bipolar separatorassembly in accordance with claim 1, wherein: the plate member comprisesa planar central area disposed between the first and second endsegments; and each of the first and second end segments includes: afirst portion co-planar with, and extending from, the central area; asecond portion following the first portion and extending transverse tothe first portion outwardly from the first surface of the first portion;and a third portion following the second portion and extendingtransverse to the second portion in a direction away from, andsubstantially parallel to, the first portion; the first and secondportions of the first end segment forming the first portion of the firstpocket, and the first and second portions of the second end segmentforming the first portion of the second pocket.
 6. A bipolar separatorassembly in accordance with claim 1, wherein: the second portion of eachof the first and second pockets is formed by an anode wet seal memberreleasably secured to the plate member; the anode wet seal memberincluding first and second legs integrally connected to one another; thesecond leg being parallel to the first leg and having a shorter lengththan the first leg; and when the anode wet seal member is releasablysecured to the respective first or second end segment of the platemember, one part of the first leg forms the second portion of therespective first or second pocket and another part of the first legextends along the third portion of the respective first or second endsegment, and the second leg of the anode wet seal member is hemmedaround the third portion of the respective first or second end segmentand abuts the second surface of the third portion of the respectivefirst or second end segment.
 7. A bipolar separator assembly inaccordance with claim 6, wherein each anode wet seal member includesfirst and second extensions at opposing sides of the first leg andextending from the one part of the first leg forming the second portionof the respective first or second pocket, so that, when the anode wetseal member is releasably secured to the plate member, the first andsecond extensions are folded toward the first portion of the respectivefirst or second end segment of the plate member to form respective endwalls of the respective first or second pocket.
 8. A bipolar separatorassembly in accordance with claim 6, wherein: each of the third andfourth pockets is formed by a cathode wet seal member separate from theplate member, and each said cathode wet seal member includes a U-shapedchannel member and an outer wet seal; the U-shaped channel member havinga bottom wall abutting the respective third or fourth end segment, a topwall opposing the bottom wall, and a sidewall connecting the top andbottom walls; and the outer wet seal positioned relative to the U-shapedchannel member so as to partially enclose the U-shaped channel memberand having a top wall abutting the top wall of the U-shaped channelmember, a sidewall abutting the sidewall of the U-shaped channel memberand opposing end walls; wherein the outer wet seal includes a centralportion and first and second corners and the heights of the opposing endwalls and of the sidewall of the outer wet seal in the first and secondcorners extend beyond the height of the central portion of the sidewallof the outer wet seal and at least up to the third portion of therespective first or second end segment of the plate member.
 9. A bipolarseparator assembly in accordance with claim 8, wherein said plate memberincludes: first and second protrusions protruding outwardly from anouter edge of the third end segment and aligned with the first andsecond end segments of the plate member so that at least a portion ofeach protrusion is co-extensive with the second portion of therespective first or second end segment; and third and fourth protrusionsprotruding outwardly from an end of the fourth end segment and alignedwith the first and second end segments of the plate member so that atleast a portion of each protrusion is co-extensive with the secondportion of the respective first or second end segment.
 10. A bipolarseparator assembly in accordance with claim 9, wherein the protrusionsare S-shaped, with a central portion of each S-shaped protrusion beingco-extensive with the second portion of the respective first and secondend segment and each sidewall of the outer wet seal of the cathode wetseal member includes an S-shaped notch to allow a corresponding S-shapedprotrusion to pass through said S-shaped notch.
 11. A bipolar separatorassembly in accordance with claim 2, wherein: said plate membercomprises a substrate formed from a first metallic material; and each ofsaid second portions of the first and second pockets and said third andfourth pockets comprises a substrate formed from one or more of saidfirst metallic material and a second metallic material different fromsaid first metallic material.
 12. A fuel cell stack assembly comprising:a plurality of fuel cells, each of the fuel cells including an anodeelectrode, a cathode electrode and an electrolyte matrix disposedbetween the anode and the cathode electrodes; a plurality of anodecurrent collectors, each anode current collector abutting a respectiveanode electrode; a plurality of cathode current collectors, each cathodecurrent collector abutting a respective cathode electrode; and one ormore bipolar separator assemblies, each bipolar separator assembly beingdisposed between adjacent fuel cells in the fuel cell stack andcomprising: a plate member having opposing first and second surfacescompatible with fuel gas and oxidant gas, respectively, the firstsurface facing an anode electrode and abutting an anode currentcollector of a first fuel cell and the second surface facing a cathodeelectrode and abutting a cathode current collector of a second fuelcell, the plate member having first and second opposing end segments andthird and fourth opposing end segments which are transverse to the firstand second opposing end segments; first and second pockets situatedadjacent the first and second end segments and extending outward of thefirst surface, wherein opposing ends of the anode current collectoradjacent the first fuel cell are inserted into respective first andsecond pockets so that the first and second pockets enclose opposingends of the anode current collector adjacent the first fuel cell; andthird and fourth pockets situated adjacent said third and fourth endsegments and extending outward of said second surface, wherein opposingends of the cathode current collector abutting the second fuel cell areinserted into respective third and fourth pockets so that said third andfourth pockets enclose opposing ends of the cathode current collectorabutting the second fuel cell; wherein the first end segment of theplate member forms a first portion of the first pocket and the secondend segment of the plate member forms a first portion of the secondpocket; wherein a second portion of the first pocket is formedseparately from the plate member and is releasably secured to the firstend segment of the plate member by being hemmed around a portion of thefirst end segment; and wherein a second portion of the second pocket isformed separately from the plate member and is releasably secured to thesecond end segment of the plate member by being hemmed around a portionof the second end segment.
 13. A fuel cell stack assembly in accordancewith claim 12, wherein: the third and fourth pockets are formedseparately from the plate member and releasably positioned adjacent thethird and fourth end segments of the plate member, respectively, so thatthe third and fourth pockets are secured at their respective positionsrelative to the plate member using pressure in the fuel cell stackassembly.
 14. A fuel cell stack assembly in accordance with claim 13,wherein: each of the third and fourth pockets is formed by a cathode wetseal member separate from the plate member and abutting the respectivethird or fourth end segment of the plate member, and each cathode wetseal member includes a U-shaped channel member and an outer wet seal,the U-shaped channel member having a bottom wall abutting the respectivethird or fourth end segment, a top wall opposing the bottom wall, and asidewall connecting the top and bottom walls, and the outer wet sealpositioned relative to the U-shaped channel member so as to partiallyenclose the U-shaped channel member and having a top wall abutting thetop wall of the U-shaped channel member, a sidewall abutting thesidewall of the U-shaped channel member and opposing end walls.
 15. Afuel cell stack assembly in accordance with claim 14, wherein: thesecond portion of each of the first and second pockets is formed by ananode wet seal member releasably secured to the plate member, the anodewet seal member including first and second legs integrally connected toone another, the second leg being parallel to the first leg and having ashorter length than the first leg, and one part of the first leg formingthe second portion of the respective first or second pocket, anotherpart of the first leg extending along the third portion of therespective first or second end segment, and the second leg of the anodewet seal member being hemmed around the third portion of the respectivefirst or second end segment and abutting the second surface of the thirdportion of the respective first or second end segment.
 16. A fuel cellstack assembly in accordance with claim 15, wherein: each anode wet sealmember includes first and second extensions at opposing sides of thefirst leg and extending from the one part of the first leg forming thesecond portion of the respective first or second pocket, so that, whenthe anode wet seal member is releasably secured to the plate member, thefirst and second extensions are folded toward the first portion of therespective first or second end segment of the plate member to formrespective end walls of the respective first or second pocket; and eachthe outer wet seal of the cathode wet seal member includes a centralportion and first and second corners extending from opposing ends of thecentral portion to form opposing corners of the respective third orfourth pocket, wherein the heights of the opposing end walls and of thesidewall of the outer wet seal in the first and second corners extendbeyond the height of the central portion of the sidewall of the outerwet seal area and at least up to the third portion of the respectivefirst or second end segment of the plate member.
 17. A fuel cell stackassembly in accordance with claim 12, wherein: said plurality of fuelcells, plurality of anode current collectors, plurality of cathodecurrent collectors and one or more bipolar plate assemblies are stackedso as to form a fuel cell stack including an anode inlet face, an anodeoutlet face, a cathode inlet face and a cathode outlet face; said fuelcell stack assembly further comprises one or more manifolds, including afirst manifold enclosing said anode inlet face and a second manifoldenclosing an anode outlet face, and one or more manifold gaskets,including a first manifold gasket disposed between said anode inlet faceand the first manifold and a second manifold gasket disposed betweensaid anode outlet face and the second manifold; and said plate memberincludes first and second protrusions protruding from an outer peripheryof the third end segment and third and fourth protrusions protrudingfrom an outer periphery of the fourth end segment, and wherein each ofsaid first, second, third and fourth protrusions is positioned so as toprotrude into the respective first or second manifold sealing gasketabutting the respective anode inlet or anode outlet face.
 18. A fuelcell stack assembly in accordance with claim 14, wherein: said platemember comprises a substrate formed from a first metallic material; andeach of said second portions of the first and second pockets and saidthird and fourth pockets comprises a substrate formed from one or moreof said first metallic material and a second metallic material differentfrom said first metallic material.
 19. A bipolar separator assembly foruse in a high temperature fuel cell comprising: a plate member includinga planar central area having opposing first and second surfacescompatible with fuel gas and oxidant gas, respectively, first and secondopposing end segments and third and fourth opposing end segments whichare transverse to the first and second opposing end segments, whereineach of the first and second end segments includes at least one bendextending along the length of the respective first and second endsegment; first and second pockets extending outward of the first surfaceof the plate member, each of said first and second pockets beingsituated adjacent the at least one bend in the first and second endsegments so that the at least one bend in the first and second endsegments prevents fuel gas from reaching comers of the plate member andfrom diffusing to said second surface of the plate member; and third andfourth pockets situated adjacent the third and fourth end segments andextending outward of said second surface of the plate member; whereinthe first end segment of the plate member forms a first portion of thefirst pocket and the second end segment of the plate member forms afirst portion of the second pocket; wherein a second portion of thefirst pocket is formed separately from the plate member and isreleasably secured to the first end segment of the plate member by beinghemmed around a portion of the first end segment; and wherein a secondportion of the second pocket is formed separately from the plate memberand is releasably secured to the second end segment of the plate memberby being hemmed around a portion of the second end segment.
 20. Thebipolar separator assembly of claim 19, wherein: the at least one bendin each of the first and second end segments of the plate memberincludes a first bend followed by a second bend; and each of the firstand second end segments includes a first portion co-planar with andextending from the central area, a second portion following the firstbend and extending transverse to the first portion outwardly from thefirst surface up to the second bend, and a third portion following thesecond bend and extending transverse to the second portion in adirection away from and substantially parallel to the first portion. 21.A bipolar separator assembly for use with a fuel cell comprising: aplate member having opposing first and second surfaces compatible withfuel gas and oxidant gas, respectively, the plate member having firstand second opposing end segments and third and fourth opposing endsegments which are transverse to the first and second opposing endsegments; first and second pockets situated adjacent the first andsecond end segments and extending outward of the first surface, thefirst and second pockets being configured to allow opposing ends of ananode current collector to be inserted into the respective first andsecond pocket so as to enclose the opposing ends of the anode currentcollector; and third and fourth pockets situated adjacent said third andfourth end segments and extending outward of said second surface, saidthird and fourth pockets being configured to allow opposing ends of acathode current collector to be inserted into the respective third andfourth pockets so as to enclose the opposing ends of the cathode currentcollector; wherein each of the third and fourth pockets is formed by acathode wet seal member separate from the plate member and abutting therespective third or fourth end segment of the plate member; and whereineach cathode wet seal member includes a U-shaped channel member and anouter wet seal, the U-shaped channel member having a bottom wallabutting the respective third or fourth end segment, a top wall opposingthe bottom wall, and a sidewall connecting the top and bottom walls, andthe outer wet seal positioned relative to the U-shaped channel member soas to partially enclose the U-shaped channel member and having a topwall abutting the top wall of the U-shaped channel member, a sidewallabutting the sidewall of the U-shaped channel member and opposing endwalls.